Turbine-blade.



W. GRUN. TURBINE BLADE. APPLICATION FILED JULY 3, 1911.

Patented May 21, 912.

WITNESSES.

WILLIBALD: GRUN', OF FRANKFORT-ON-THE-MAIN, GERMANY.

TURBINE-BLADE.

Specification of Letters Patent.

Patented May 21, 1912.

' Application filed July 8, 1911. Serial No. 637,503.

To all whom it may concern:

Be it known that I, WILL IBALD GRUN, a citizen of the German Empire, anda resident of Frankfort-on-the-Main, Germany, have invented certain newand useful Improvements in Turbine-Blades, of which the following is aspecification.

My present invention relates to rotating turbine blades and has for itsobject to so construct them as to reduce or avoid the detrimentaleffects due particularly to the action of centrifugal force.

In rotary turbine blades as generally constructed with recesses at theinner portion or foot, the center of gravity of the root cross sectionof the blade (that is to say, the cross section of the blade at thepoint where it projects from the turbine wheel) is not located in thesame radial line with the center of gravity of the outer blade portionor blade body, that is to say, the portion extending outwardly from thewheel. Owing to this unfavorable arrangement, the centrifugal forcearising during the operation of the turbine will tend to bend theblades, the bending strain falling most heavily on the junction of thefoot with the outer portion or body of the blade, and many bladefractures are due to this cause.

According to my present invention, the blades are inclined in such amanner that their concave or impact-receiving surfaces will form obtuseangles with the respective tangents to the wheel. This arrangementenables me to bring the center of gravity of the root cross sectionexactly or approximately into the same radial line with the center ofgravity of the outer or body portion of the blade.

In the accompanying drawing, Figures 1, 2 and 3 are fragmentary views,with parts in section, showing three different constructions of bladesembodying my invention.

The body of the wheel or rotor is indicated at g, and its center at f.The outer circumference of the wheel, at 6-0, indicates the plane of theroot cross section of the blade, which has a notched portion fitted intothe wheel body 9. The outer or bodyv portion of the blade receives theimpact of the steam or other driving medium. I have not illustrated thedetails of-the manner of fitting the blades to the wheel, as any usualor approved construction may be employed. In the constructionsillustrated by Fig. 1,

the center of gravity of the root cross section is indicated at 6, whiled is the center of gravity of the body portion a. It will be seen thatthese two centers of gravity are located upon the same radius f, 6, cl.In

order to accomplish this result, the blades instead of being setradially as in ordinary practice (that is to say,at an angle of 90 tothe periphery) are so arranged that their concave or impact-receivingsurfaces (facing toward the left in the drawing) will form obtuseangles, as 90+oa, with the periphery,

that is to say, with the respective tangents to the wheels periphery.

The blade bodies a taper toward their outer ends. In the constructionshown in Fig. 2, the blade bodies a are of uniform thickness, butotherwisethe arrangement is the same, that is to say, the concaveimpactreceiving front surfaces form obtuse angles with the respectivetangents to the wheels periphery, or, to express it in a different way,the convex back surfaces form acute angles wit-h such tangents, and thetwo centers of gravity 6' and d are located on the same radius. Withthis arrangement of the two centers of gravity, the bending strainotherwise produced at the root cross section by the action ofcentrifugal force, is avoided entirely. Even when the two centers 0gravity are only approximately on the same radius, a considerableadvantage is secured over the usual construction, with radial blades,since the bending strain due to the action of centrifugal force isminimized.

During the operation of the turbine (which in the constructionillustrated will rotate clockwise) the pressure of the driving medium onthe blades will tend to bend them (clockwise) relatively to the rootcross section. To counteract this tendency, the obtuse angle at whichthe blades are inclined to the wheels periphery may be increased ,(asshown in Fig. 3) so that the center of gravity 6 of the root crosssection will be in the rear (to the left in the drawing) of the radiusf, d which passes through the center of gravity 0? of the blade body of.

tend to bend the blade body contra-clockwise, that is to say, contraryto the bending act-ion due to steam pressure, and the two tendencies maybe made to neutralize each other absolutely or approximately. It willtherefore be understood that the useful result pointed out above isobtained whenever the two centers of gravity are in the same radialregion, Whether actually or approximately on the same radius; thus it isnot essential to my invention to bring the aforesaid two centers ofgravity exactly into the same radial line, since the diminution oravoidance of bending strains is often attained even better if the centerof gravity of the root cross section is slightly to one side of theradius passing through the center of gravity of the blade body.

Various modifications may be made Without departing from the nature ofmy invention as set forth in the appended claims.

I claim as my invention:

1. In a turbine, a rotor comprising a Wheel and blades carried thereby,the impact-receiving surfaces of the blades forming obtuse angles Withthe respective tangents to the periphery of the Wheel.

2. In a turbine, a rotor comprising a Wheel and inclined blades carriedthereby, the center of gravity of the root cross sec tion of a blade andthe center of gravity of the body of the same blade being located in thesame radial region of the Wheel.

3. In a turbine, a rotor comprising a Wheel and inclined blades carriedthereby, the center of gravity of the root cross section of a bladebeing in the rear of the radial line drawn through the center of gravityof the body of the blade.

In testimony whereof I have signed this specification in the presence oftwo subscriblng witnesses.

IVI'LLIBALD GRUN.

Witnesses JEAN GRUND, CARL GRUND.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents, Washington, I). C.

